Video conferencing room design

Inhalt:

Preparations

Previous to the conference each participant should check the recording level of his audio signal and monitor it during the conference. Video conference programmes usually have recording level displays for this purpose. The red area should be reached for short periods of time while speaking.

Audio

low-noise room to suppress reverberation and acoustic feedback
Minimise background noise (remove devices, close windows).
walls and ceilings without reflection (textile covered or rough-textured)
floor without reflection (textile floor covering)
If there is a fixed public address system a galvanic separation with an isolating transformer to avoid buzzing sounds is recommendable.
Distance between loudspeaker and microphone at least five times of distance between speaker and microphone.
Loudspeaker should be set to the lowest sensitivity of the microphone (mostly behind the microphone).
Directional microphones are not recommended, as they record to much background noise.
For individual people the use of a headset is recommended, giving a smaller and constant distance to the microphone. Thus there is hardly any acoustic feedback.
For groups a sensitive (dynamic) microphone is recommended, which the speaker approaches. For table microphones an active echo suppression or, when several table microphones are used, an automatic mixer is necessary.
When boundary layer microphones are used it is necessary for all people to sit directly at the table and avoid hits or knocks to the table with feet, chairs, pens etc.
A low acoustic feedback of the audio signal from loudspeaker to microphone can give the partner the feeling of a time delay in the transmission: own speech reaches the speaker 1 to 3 seconds later. If this acoustic feedback is too loud, the speaker is hindered in his flow of words, since he is cut off by himself all the time. If the stability limit is exceeded, there is a loud rhythmic soughing sound.
Only a good leveling of the audio signal ensures a good quality of the volume, since at a transmission rate of 8 bits resolution there are hardly any reserves.
In bigger rooms with more than one work places the mutual interference can be minimised by separating the video conference area.
Switch off microphone in group conferences if the participants are silent for a longer time.

Video

much light (noise of the signal becomes less)
background not to light, otherwise people appear too dark
grey background prevents coloured reflections
no patterns in background (these would cause unnecessary data rates or interferences)

Light

from the front or diagonally from the front
no moving shadows should be thrown on the background
if the light comes from the side only one half of the face might be visible
in backlight people are displayed too dark
soft light is advantageous, can be achieved by extensive or indirect illumination

Accessories

Mixer
If more then one microphone or more than one PC is used a mixer for the distribution of the audio signal is necessary. In order to distribute signals from and to the PC a professional mixer with an adjustable monitor cable, directing all signals to the mixer, is necessary. There the user can set up which signals are recorded at the PC and which are put out by the loudspeaker. By lowering the bases and a slight raising of the middle frequences the speech becomes more clearly. With the use of a mixer it is possible to correct the recording level directly and without software. Thus a quick and independent volume regulation is possible.
Loudspeakers
In comparison to external PC loudspeakers professional active loudspeakers have a clearer sound and are more robust. Passive loundspeakers (without an integrated amplifier) are not to be recommended because they are lacking volume regulation, although their output is sufficient for many cases of operation.
Extensions and Adapter

Since the interface area of the PCs is difficult to reach it is useful to put the supplies for headphones and microphone on the table with an extension cable. The quality of sound was not affected by this.

Projection walls
For further directions for the arrangement of furniture in different situations see:
Bretford's Guide to successfully planning a video conferencing room